Multilocus enzyme systems are a common and important feature of the human and mammalian genome. This research proposal is concerned with an in-depth multifaceted investigation of the biochemical genetics of the human alkaline phosphatases (ALPs) which represent a model example of such a system. At least three loci occur and they are differentially expressed in different tissues. Differences between the enzyme products of the several loci obtained from various human tissues (placenta, liver, kidney, bone and adult and fetal intenstine) will be characterized in detail by inhibition studies using a series of aminoacid and peptide inhibitors; by electrophoresis; by thermostability studies; by cross-reactivity studies using conventional antisera; and with monoclonal antibodies prepared by the mouse hybridoma technique, which will allow us to ask whether a particular antigenic determinant present on one ALP is present or absent on another. Similar studies will be carried out on ALPs from different tissues of other animal species. These investigations will enable us to analyze in detail the interrelationships of the several ALP loci both in man and other species, and identify the points in ALP evolution when gene duplications occurred. Certain malignancies and cell lines derived from malignancies show aberrant expression of an ALP locus not normally expressed in the tissue of origin. An extensive series of malignant cell lines will be examined to find out how often this occurs; which loci are aberrantly expressed; and whether the phenomenon is peculiar to some malignancies rather than others. In addition the aberrantly expressed ALPs will be characterized in detail to identify differences from the corresponding normal ALP, which might have arisen by mutations or by specific post-translational changes occurring in the malignant cells. Other related investigations will include the search using monoclonal antibodies for ALP polymorphisms not detectable by electrophoresis; and studies of the specific deficiency of liver/bone/kidney ALP in hypophosphatasia to determine whether cross-reacting but enzymically inactive protein is produced by the mutant allele, and whether there is genetic heterogeneity.